Hey guys. I know I haven't posted anything here in a while, but I've been busy and I need some ideas for things to look at on my 'burban. This was the first place I thought of to ask. First off, it's a 98 1500 4x4, 5.7, mostly stock. Had the truck since January of this year. Ran like crap, but it's running almost new now. Although there are still a few issues I can't figure out. Here's what has been done so far... New Magnaflow cats (dual exhaust) Used Flowmaster mufflers 3 new O2 sensors, 4th one wasn't throwing a code (it's the one after the cat on driver side) New plugs, wires, cap, etc New thermostat (3 times) New temp sensors (one in thermostat housing, one in block on driver side) New fuel injectors (the upgrade mpfi setup) New air filter A couple oil changes (just because I drive it every day) Cleaned plenum and upper intake when I changed injectors Cleaned MAF sensor with that MAF sensor spray stuff (can't think of the name right now) New PCV valve I think that's it. If I think of anything I'll put it in a new post. Here's the issue... When I first start it, the engine wants to hesitate a little. After about 2 or 3 minutes it clears up. Doesn't matter if the engine is cold or warmed up. If I turn it off, it does it again upon startup. Could have only been sitting 5 minutes and it'll do it. After it clears, she runs like a champ. Still throwing lean codes on bank 2, the reason I changed out both O2 sensors on that side. I inspected the wires and from what I can see of them they look fine. Even took a look a some vacuum lines and the few that I found looked good. Second issue, going by the gauge, when it's warming up, the temp goes up to about 255 deg before the thermostat opens. After that, it goes back down to 210, then up to 220 and stays. 3 different thermostats did the same thing. I replaced the temp sensors because one of them was not working properly. Gauge would never get past 125 deg. Some of the research I did said this may be causing the lean issue, but it's still doing it. Thinking one of those may be an out of box failure, but I'm not sure. Sorry for the long post, but as you can tell, I've got a couple issues and running out of things to check. Any help would be greatly appreciated.